Solar battery powered watch

ABSTRACT

A covering member (4), a solar battery (3) and a hand-operating mechanism-containing movement (2) are housed inside a case (1) which has a front side opening (1a), a glass (5) which is provided in the front side opening (1a), in the order of these constituents from the face side of the case (1). The solar battery (3) is disposed opposite to the glass (5) at a light receiving surface thereof which is covered with the covering member (4). The covering member (4) can also serve as a dial. If the covering member (4) is molded out of ceramic, it can provide the dial with a white appearance, so that light can sufficiently be transmitted to the receiving surface of the solar battery (3) owing to the light transmittance of the ceramic.

TECHNICAL FIELD

This invention relates to a solar battery powered watch provided with asolar battery as a power supply.

BACKGROUND TECHNOLOGY

A solar battery powered watch provided with a solar battery as a powersupply has been conventionally generally structured in a manner that thesolar battery is mounted on the surface of a dial under a glass so as tobe seen from the outside in view of the fact that the solar batteryabsorbs light to generate electric power.

However in such a structure, since the solar battery has a peculiar deepviolet color, colors of the dial and designs of the dial are largelyrestricted, which makes it difficult to bring out an ornamental value ofthe watch.

Aiming to solve such a problem, there is proposed an invention havingcoloring means at a light receiving surface of a solar battery asdisclosed, for example, in a publication of JP-A 5-29641.

That is, in the same publication, cholesteric liquid crystal ismicrocapsuled and the surface of the solar battery is coated with themicrocapsuled liquid crystal as a binder.

However, in the coloring means disclosed in the same publication, thereare few colors to be selected as those of the dial, and the surface ofthe dial becomes a deep color, and hence it does not enhance theornamental value thereof. Particularly, there is a problem that theaforementioned coloring means can not produce white which is a basiccolor and is frequently used as a color of the dial of the watch.

Under the circumstances, it is an object of this invention to realize asolar battery powered watch capable of designing a dial with free colorsincluding white, and of transmitting light which is sufficientlynecessary for generating electric power for the solar battery.

It is another object of this invention to provide a solar batterypowered watch capable of improving impact resistance of a coveringmember.

DISCLOSURE OF THE INVENTION

To achieve the above objects, a solar battery powered watch of thisinvention comprises a case having an opening on a front side thereof,and a glass covering the opening, a movement having a hand-drivingmechanism and housed in the case, a solar battery having a lightreceiving surface disposed opposite to the glass and installed on afront side of the movement inside the case, and a covering member forcovering the light receiving surface of the solar battery.

With such an arrangement, since the surface of the covering member canbe seen from the outside through the glass, if the covering member isalso used as the dial, it is possible to provide the solar batterypowered watch provided with a dial having a desired color if the colorof the covering member is adjusted to the desired color.

According, to this invention, the covering member is molded out ofceramic. Since the ceramic in general looks white, it is possible toform white dial (covering member) without coloring the dial.

It is needless to say that the covering member molded out of ceramic canprevent the solar battery from being seen from the outside. Further,since incident light appropriately is transmitted through the ceramicmade of a porous material, the solar battery can be charged without aproblem.

Since ceramic is easily colored, its color other than white is freelyadjustable.

Further, this invention provides a solar battery powered watch havinglight transmittance so that the solar battery is irradiated withsufficient light, and a preferable structure of the covering member toshow a white appearance.

That is, if the covering member is molded out of ceramic containingaluminum as a main constituent, it can show a preferable white, and ifan average diameter of the ceramic grains ranges from 5 μm to 40 μm, andthe covering member is molded to a thickness ranging from 0.2 m to 0.5mm, the covering member can keep high external quality and transmitlight sufficiently for charging the solar battery.

In case that the covering member its utilized as a dial, dial patternssuch as an indicator, lettering for a brand name, and the like areinscribed on the surface of the covering member. As a result, since thelight transmittance is prevented by the dial patterns, it is unavoidablethat light transmittance area of the covering member is reduced.Further, light returned to the surface of the covering member owing todiffusion of light in the covering member is absorbed by an interfacebetween the covering member and the dial patterns so that the amount oflight which reaches the solar battery is further reduced.

Accordingly, it is preferable to form an arbitrary dial patterns on thesurface of the covering member and to interpose light reflection layersor light reflection faces between the surface of the covering member andthe dial patterns to keep the watch driving stable by minimizing thereduction of the amount of irradiation of light to the solar battery.

In such a structure, light which is incident on the covering member asthe dial first enters the inside of the covering member which is lighttransmittant. The thus entered light is diffused inside the coveringmember and directed to various directions. As a result, most of theincident light spreads out while it is diffused inside the coveringmember, and a part of the incident light is returned to the surface ofthe covering member.

The amount of light which is returned to the surface is substantiallyuniform on the surface of the covering member. Since the light returnedto a part where the dial patterns are formed is reflected on the lightreflection layers or light reflection faces, and it is returned to theinside of the covering member, and then it is transmitted to the solarbattery, the amount of irradiation of light to the solar battery can beincreased.

In the case of the conventional solar battery powered watch having noreflection layer at the interface between the covering member and thedial patterns, the light returned to the part where the dial patternsare formed inside the covering member is all absorbed by the dialpatterns. In such a manner, since the light which spreads out while itis diffused inside the dial is absorbed by the dial patterns, and hencethe amount of irradiation of light to the solar battery is significantlyreduced.

The arrangement of the solar battery powered watch having lightreflection layers or light reflection faces can eliminate the loss oflight caused by the light absorption at the interface between thecovering member and the dial patterns, and can reduce the loss in theamount of irradiation of light.

It may be possible to laminate a transparent substrate to the surface ofthe covering member, and to form arbitrary patterns on the surface ofthe transparent substrate, and further light reflection layers or lightreflection faces are interposed between the surface of the transparentsubstrate and the dial patterns. Since the covering member is molded outof ceramic, it has a property that it is fragile and breaks easily whenimpact loading is applied to the covering member. Particularly, when thecovering member is accommodated to move freely in the case, there isgood possibility that the covering member strikes strong against aperipheral sidewall of the opening of the case and that it is brokenwhen an impact loading is applied.

Accordingly, it is preferable that the outer rim of the covering memberis in contact in advance with the peripheral sidewall of the opening ofthe case, whereby the movement of the covering member in the case isrestricted to prevent the breakage of the covering member.

Further, if at least the outer rim of the covering member is pressedagainst the peripheral sidewall of the opening of the case by an elasticmember, the covering member can be surely brought into contact with theperipheral sidewall of the opening of the case.

In order to carry out the positioning of the covering member utilizableas the dial in the case, it may be possible to dispose a positioningframe around the outer periphery of the covering member, to provideprojecting parts or recessed parts in the positioning frame, to providerecessed parts or projecting parts in the covering member for engagementwith the projecting parts or recessed parts of the positioning frame,and to provide positioning means for positioning the positioning framerelative to the movement.

With such an arrangement, the covering member can be easily positionedrelative to the movement, which becomes a positioning standard relativeto respective constituents in the case, by way of the positioning frame.

An ornamental frame may be provided inside the case along the rim of theopening of the case for enhancing the value of the watch as ornamentalgoods.

In this case, when the inside of the periphery of the covering member isbrought into contact with the ornamental frame, the movement of thecovering member is restricted inside the case to prevent the breakage ofthe covering member.

Further, when the positioning projecting parts are provided on theperiphery of the covering member, if a gap is defined between theperiphery of the covering member and the case, and the projecting partsprovided on the periphery of the covering member are disposed in thegap, the projecting parts do not contact the case. Accordingly, even ifthe covering member receives an impact loading, there is no likelihoodof occurrence of stress concentration the projecting parts, so that thetolerance against an impact can be further enhanced.

In the solar battery powered watch which is structured such that theopening formed at the back side of the case is covered by a case back,and the covering member, the solar battery and the movement are held bya casing frame, it is preferable to interpose an intermediate membermade of a resin material between the case back and the movement.

As a result, when the solar battery powered watch receives an impactloading, the intermediate member functions to suppress the deformationof the covering member, thereby preventing the breakage of the coveringmember with more reliability.

If the intermediate member is disposed at a position opposite to theornamental frame, there is no possibility that a shearing force acts onthe covering member which is held between the ornamental frame and theintermediate member, thereby preventing the breakage of the coveringmember with more reliability.

Further, even if an elastic member is interposed between the case backand the casing frame, the elastic member functions to suppress thedeformation of the covering member, thereby preventing the breakage ofthe covering member with more reliability.

For positioning the covering member relative to the movement, it may bestructured such that through holes are defined in the covering member ata region contacting the ornamental frame, and end portions of the fixedpins are engaged in the through holes, and the fixed pins protrude fromthe underside of the covering member, and through holes are defined inthe solar battery for insertion of the fixed pins, and further a meansfor securely holding the fixed pins is provided on the movement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a solar battery powered watchaccording to a first embodiment of this invention.

FIG. 2 is a plan view of a covering member which is one of theconstituents of the solar battery powered watch of the first embodimentand is used as a dial.

FIG. 3 is a table showing a condition for fabricating the coveringmember, average diameters of ceramic grains, and results of measurementof transmittance and transparency of each sample.

FIG. 4 is a plan view of a dial (covering member) of a solar batterypowered watch according to a second embodiment of this invention.

FIG. 5 is a cross sectional view taken along the line A--A of FIG. 4.

FIGS. 6 through 9 are cross sectional views for explaining function andeffect of the solar battery powered watch according to the secondembodiment of this invention.

FIG. 10 is a cross sectional view of a solar battery powered watchaccording to a third embodiment of this invention.

FIG. 11 is a plan view of a covering member which is one of theconstituents of the solar battery powered watch of the third embodimentand is used as a dial.

FIG. 12 is a cross sectional view of the solar battery powered watchaccording to a modification of the third embodiment of this invention.

FIG. 13 is a cross sectional view of the solar battery powered watchaccording to another modification of the third embodiment of thisinvention.

FIG. 14 is a cross sectional view of a solar battery powered watchaccording to a fourth embodiment of this invention.

FIG. 15 is a plan view of a covering member which is one of theconstituents of the solar battery powered watch of the fourth embodimentand is used as a dial.

FIG. 16 is a cross sectional view of the solar battery powered watchaccording to a modification of the fourth embodiment of this invention.

FIG. 17 is a cross sectional view of the solar battery powered watchaccording to another modification of the fourth embodiment of thisinvention.

FIG. 18 is a cross sectional view of the solar battery powered watchaccording to still another modification of the fourth embodiment of thisinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

A best mode for carrying out this invention will be now described withreference to the attached drawings.

(First Embodiment)

A solar battery powered watch according to a first embodiment of thisinvention will be now described with reference to FIGS. 1 and 2. FIG. 1is a cross sectional view of the solar battery powered watch accordingto the first embodiment of this invention, and FIG. 2 is a plan view ofa covering member which is one of the constituents of the solar batterypowered watch of the first embodiment and is used as a dial.

As shown in FIG. 1, the solar battery powered watch accommodates amovement 2, a solar battery 3, and a dial 4 in a case 1.

The case 1 has an opening (face side opening) 1a at the front sidethereof, and another opening (back side opening) 1b at the back sidethereof. A glass 5 made of transparent glass or sapphire is provided inthe face side opening 1a. Meanwhile, the back side opening 1b can becovered by a case back 6. Respective constituents in the case 1 can beaccommodated through the back side opening 1b.

Respective constituents in the case 1 are arranged in the order of thedial 4, the solar battery 3 and the movement 2 from the side close tothe glass 5, wherein a light receiving surface (front surface) 3a of thesolar battery 3 is opposed to the glass 5.

The movement 2 houses therein an electric double layer capacitor forstoring a generated electric power of the solar battery 3, a crystaloscillator serving as a time base source, a semiconductor integratedcircuit for generating driving pulses for driving a hand 7 based on anoscillation frequency of the crystal oscillator, a step motor fordriving a train wheel mechanism second by second upon reception of thedriving pulses, and the train wheel mechanism, which are respectivelynot shown.

The dial 4 serves as a covering member for covering the surface of thesolar battery 3, described later, so that the solar battery 3 can not beseen from the outside. Dial patterns such as an indicator, lettering fora brand name, and the like are inscribed on the surface of the dial 4for performing a primary function of the inherent dial 4.

The dial 4 is in advance fixed to the movement 2 by way of a positioningframe 8. That is, as shown in FIG. 2, positioning pins 2a and 2b areprovided on the movement 2 at the front periphery thereof, and thepositioning pins 2a and 2b penetrate the solar battery 3 and protrudefrom the positioning frame 8 at their arranging portions (frontperiphery of the solar battery 3). Meanwhile, positioning holes 8a and8b are bored in the positioning frame 8. When the positioning pins 2aand 2b are engaged in the positioning holes 8a and 8b, the positioningframe 8 can be fixed to the movement 2 at a given relative positionthereof.

Further, recessed parts 8c and 8d are provided on the positioning frame8 at the inner periphery thereof, while projecting parts 4a and 4b areprovided on the dial 4 at the outer periphery thereof. When theprojecting parts 4a and 4b are engaged. in the recessed parts 8c and 8d,the dial 4 can be fixed to the positioning frame 8.

The dial (covering member) 4 is formed by molding ceramic containingalumina and zirconia as a main constituent. Particularly, in the firstembodiment, the dial 4 is made of ceramic containing alumina as the mainconstituent. The ceramic made of alumina as the main constituents looksa preferable white, and has high mechanical strength.

If the dial 4 is to be colored, pigment is dispersed in the ceramic orthe surface of the dial 4 is colored by coating means so that the dial 4is easily colored with a desired color.

The solar battery 3 is formed of thin films of non-monocrystallinesilicon or films of monocrystalline silicon, or films of compound

In the first embodiment, the light receiving surface 3a of the solarbattery 3 is covered with the dial 4, causing the light receivingsurface 3a to be unrecognizable from the outside. Accordingly, thepeculiar deep violet color of the solar battery 3 can not be seen, andhence the dial 4 looks white which is particular to alumina.

Although it is sufficient that the dial 4 and the solar battery 3 aremerely overlapping each other, they can be joint to each other by atransparent adhesive, and the like in an assembling step thereof, ifnecessary.

A method of fabricating the solar battery 3 will be now described.

First, an insulating film (not shown) is formed on the entire surface ofa metallic substrate made of e.g., brass by use of a sputtering system,The insulating film is made of silicon oxide in the thickness of about100 nm.

Next, an electrode film (not shown) is formed by use of the samesputtering system. The electrode film employs aluminum containing, e.g.,1 wt % of silicon. The electrode film may be formed on the entiresurface of the metallic substrate or may be partly formed on theinsulating film.

When the electrode film is partly formed on the insulating film, a metalmask is employed. The metal mask is formed of a thin sheet of a metallicmaterial, and has an opening in a region forming the electrode. Themetal mask having the opening therein is put on the substrate, and it isarranged in the sputtering system, then the electrode film is formed inthe opening of the metal mask.

Subsequently, a solar battery layer (not shown) composed of thin filmsof non-monocrystalline silicon is formed on the surface of the electrodefilm. The solar battery layer is composed of, for example, amorphoussilicon films (non-monocrystalline silicon films) each having astructure of a p-i-n type conductivity.

The solar battery layer is formed by use of a plasma chemical vapordeposition system. Silane gas (SiH₄) is used as reactive gas. Anamorphous silicon film of n-type conductivity is formed by addingphosphine gas (PH₃) as dopant, and an amorphous silicon film of p-typeconductivity is formed by adding diborane gas (B₂ H₆) as dopant. Ani-type amorphous silicon film may be formed without adding any dopant.

The thickness of the p-type film, and the n-type film, respectively,ranges from 50 to 100 nm, and the thickness of the i-type film rangesfrom 50 to 300 nm.

The solar battery layer composed of the amorphous silicon films of p-i-njunction can be formed continuously with the plasma chemical vapordeposition system.

Then, a transparent electrode film (not shown) is formed on the surfaceof the solar battery layer by use of the sputtering system, therebyobtaining a solar battery 3. In forming the transparent electrode film,indium tin oxide (ITO) is used.

The metal mask may be used for forming the transparent electrode film onparts of the surface of the solar battery layer. The metal mask isprepared from a thin metal sheet and has openings in regions where thetransparent electrode film is formed. The formation of the transparentelectrode film within the openings of the metal film is carried out byplacing the solar battery inside the sputtering system, where the layerof the solar battery is overlaid with the metal mask having theopenings.

A method of fabricating the dial 4 formed by molding ceramic containingalumina as a main constituent is described hereafter.

Firstly, a mold is filled up with a mixture of a ceramic materialcontaining alumina as a main constituent, and a binder. In this case,alumina in powder form of about 0.3 μm in grain diameter is used, and anamount of the binder added represents about 3.0% of the mixture.

For the ceramic material, alumina at purity of 99.5% or higher is used,and for the binder, polyvinyl alcohol (PVA) is used.

In the case of the ceramic material of alumina at a purity less than99.5% being used, the dial 4 was found tinted with the color ofimpurities, significantly reducing declining its light transmittance.Therefore, it is preferable to use the ceramic material of high purityalumina at 99.5% or higher for fabricating the dial 4 for a desirablewhite appearance.

Then, a pressurizing process is applied to the mold filled up with themixture of the ceramic material and the binder. At this time, pressureof about 1 ton/cm² is applied to the mold.

Hereupon, as shown in FIG. 2, the dial 4 has projecting parts 4a and 4b,a display window 4c for displaying dates and days of the week, and acenter hole 4d through which a spindle of the second hand protrudes froma movement of the watch.

Subsequently, a first sintering process is applied to the dial 4,removing the binder composed of PVA which was added to the ceramicmaterial. The first sintering process is applied in the atmosphere at atemperature in the range of about 800° to 1600° C. for a duration ofabout 120 minutes. As a result of the first sintering process applied,the dial 4 shrinks slightly in its outer dimensions because the binderis removed, but undergoes little change in the thickness thereof.

Thereafter, a second sintering process is applied at a temperaturehigher than that for the first sintering process. The second sinteringprocess is applied at a temperature (1500° to 1900° C.) close to thefusion point of ceramic for a duration of about 300 minutes. The secondsintering process is applied in a vacuum to increase the density of theceramic.

The second sintering process applied at a temperature close to thefusion point of the ceramic as described above is conductive to progressin crystallization. Consequently, the diameter of the ceramic grains inthe final stage of the steps is much larger than 0.3 μm.

By means of such a step of enlarging the diameter of the ceramic grainsas described above (crystallization step), light transmittance of theceramic can be enhanced. The enhanced light transmittance of the dial 4permits a sufficient amount of light to be transmitted to the solarbattery 3, which is quite desirable from the viewpoint of securingenough generated power necessary as a source of power supply to thewatch.

However, it has been found as a result of various studies that the stepof enlarging the diameter of the ceramic grains applied excessivelyresults in excessive transparency of the dial 4 due to a decrease in aamount of light scattered inside the ceramic. When the dial 4 becomesexcessively transparent, it can not fulfill its function as a coveringmember to cause the solar battery to be unrecognizable from the outside.

In this embodiment, a preferable diameter of the ceramic grains informing the dial 4 will be described later. However, prior to thisdescription, steps to be taken upon completion of the second sinteringprocess will be first described.

Upon completion of the second sintering process, the surface of the dial4 is flattened by removing undulation thereof by use of a grinder. Thereare various methods of grinding, for example, simultaneous grinding ofboth faces, grinding of one face by pasting the ceramic on a working jigusing wax, and the like. For grinding, diamond powders and a diamondgrinder are used.

As for the size of a workpiece in grinding, it is preferable to adopt athickness in the order of 0.4 mm. Normally, the thickness of theworkpiece when the pressurizing process thereof in the mold is completedmay be preferably thicker by about 0.3 mm than that of the finished dial4.

Then, a third sintering process is applied to the ceramic at atemperature (1200° to 1600° C.) lower than that for the second sinteringprocess for a duration of about 120 minutes. By applying the thirdsintering process in the atmosphere, dirt adhered to the surface of theceramic is removed through oxidation reaction, and the like.

Then, barrel polishing is applied to the dial 4 by use of a barrelpolishing apparatus. In such barrel polishing, balls made of copper (Cu)may be used. As a result of the barrel polishing, the surface roughnessof the dial 4 is reduced thereby, enhancing the light transmittance ofthe dial 4. Furthermore, the barrel polishing enables burrs generatedaround the outer rim and in the corners of the dial 4 to be removed andin addition, roundness to be provided in the corners of the dial 4.

Thereafter, a fourth sintering process is applied to the ceramic at atemperature (1200° to 1600° C.) lower than that for the second sinteringprocess for a duration of about 120 minutes. The fourth sinteringprocess is also applied in the atmosphere for cleaning up the surface ofthe ceramic by further removing dirt adhered to the surface. Normally,the third and fourth sintering processes may be applied under the samecondition.

Finally, indicators, lettering for a brand name and the like, graphic, asymbol (dial patterns) are inscribed on the surface of the dial 4 by aprinting method to complete the dial 4.

In case that undulation on the surface of the ceramic, and fluctuationin the thickness thereof can be minimized in the course of thepressurization process of the ceramic using the mold, and the first andsecond sintering processes thereof, the grinding and the third sinteringprocesses to be applied thereafter may be omitted.

The inventors of this application fabricated samples (A to M) of thedial 4 by use of the method of fabrication under varying conditions.FIG. 3 shows fabricating conditions of the samples, and measurementresults of samples including average diameters of ceramic grains of thesamples, light transmittance of respective samples, and transparency ofthe same.

Alumina used in fabrication of the samples was 99.9% pure, and thethickness of the samples (A to M) of the dial was 0.4 mm. As a result ofthe second sintering process applied in vacuum, the ceramic of each ofthe samples acquired high density in the range of 3.90 to 3.92 g/cm³.

The average diameters of the ceramic grains were measured throughobservation of the cleaved surfaces of the samples using an electronmicroscope. The light transmittances of the samples were determined bymeasuring a power output value of the solar battery 3 when the samples(A to M) of the dial were placed on the solar battery 3. Herein, thelight transmittance was determined as 100% when a power output value ofthe solar battery 3 without the samples (A to M) of the dial placedthereon was obtained.

Further, transparency of the samples (A to M) of the dial was determinedby visual observation therethrough on the basis whether or not two blacklines drawn in parallel at a spacing of 0.3 mm can be separablyidentified. Some of the samples, through which such identification wasachieved, are marked with blank circles while other samples are markedwith crosses. The spacing of 0.3 mm between the two black linescorresponds to the size of smallest letters normally inscribed on thedial of a watch.

As is evident from the measurement results shown in FIG. 3, when theaverage diameter of the ceramic grains is 45 μm or greater, thetransparency of the dial samples increases excessively, significantlyreducing the dial's performance to cover the solar battery 3. Theresults of a survey made on sensuous impression of a plurality ofsubjects actually inspecting a solar battery powered watch fabricatedaccording to the structure shown in FIG. 1 indicate that the criteriafor assessing the transparency, adopted by the inventors of theinvention, substantially agree with the subjects' sensuous perception onthe transparency.

It has been found from the measurement results described above that theaverage diameter of the ceramic grains need be preferably kept at about40 μm or less for the dial 4 to permit a maximum amount of lightirradiating the solar battery 3 to be transmitted therethrough, and yetto cover sufficiently the solar battery 3.

On the other hand, it has become apparent that when the average diameterof the ceramic grains becomes less than 5 μm, the light transmittance ofthe dial declines sharply. Accordingly, it can be stated that theaverage diameter of the ceramic grains need be preferably kept in therange from 5 μm to 40 μm for the dial 4 to obtain whiteness whilepermitting the solar battery 3 to maintain a necessary power generationcapability.

Further, the thickness of the dial 4 is preferably kept in the rangebetween 0.2 mm and 0.5 mm because impact resistance thereof deteriorateswhen the thickness becomes less than 0.2 mm. On the other hand, when thethickness is greater than 0.5 mm, the watch itself becomes excessivelythick, depreciating the commercial value thereof. However, from theviewpoint of strength, the dial 4 with the critical thickness of 0.1 mmat the minimum can be put to practical use.

Reviewing again the measurement results shown in FIG. 3 while takinginto account such constraint as described above in respect of thethickness of the dial 4, it can be stated that, as the dial 4 becamethinner by 0.1 mm, the light transmittance thereof increased by about1.5%, but that the transparency thereof did not undergo noticeablechange.

Therefore, it is appropriate to state that the average diameter of theceramic grains should be preferably in the range from 5 μm to 40 μmregardless of the thickness of the dial 4 provided that the thicknessthereof is in the range between 0.1 mm and 0.5 mm.

Further, it is readily understood on the basis of the measurementresults shown in FIG. 3 that the average diameter of the ceramic grainscan the controlled by regulating sintering temperatures, the duration ofsintering, sintering atmosphere, and the like.

When the dial 4 fabrIcated under the adequate conditions described abovewas incorporated in the solar battery powered watch having the structureshown in FIG. 1, the watch was found to continue moving normally withoutstopping due to shortage of generated electric power. Furthermore, thedial 4 was natural white in color.

(Second Embodiment)

A solar battery powered watch according to a second embodiment will benow described.

The feature of the second embodiment resides in a structure of dialpatterns which are formed on the surface of a dial (covering member) 4of the solar battery powered watch shown in FIG. 1. The other entirestructure and the method of fabricating the solar battery, and themethod of fabricating the dial are the same as those of the firstembodiment (see FIG. 1), and hence the detailed explanations thereof areomitted while numerals in figures are denoted in common with those ofthe first embodiment.

FIG. 4 is a plan view of a front surface of the dial, and FIG. 5 is across sectional view taken along the line A--A in FIG. 4.

As shown in FIG. 4, dial patterns 10 such as indicators, lettering for abrand name and the like, graphic, a symbol are inscribed on the surfaceof the dial 4.

As shown in FIG. 5, light reflection layers 11 are interposed betweenthe surface of the dial 4 and the dial patterns 10. The light reflectionlayers 11 are formed by masking the surface of the dial 4, then applyinga vacuum evaporation to a thin metal film such as aluminum, nickel, andthe like or etching the thin metal film formed on the entire surface ofthe dial 4 in the form of the dial patterns 10. After the lightreflection layers 11 were formed, the dial patterns 10 may be printed onthe surface of the light reflection layers 11. Further, the dialpatterns 10 may be printed using ink in which fine particles of gold oraluminum is dispersed, then heat drying or high temperature sinteringprocess is applied to the dial patterns 10 so as to form the lightreflection layers 11.

The effect of the formation of the light reflection layers 11 will benow described with reference to FIGS. 6 through 8.

FIG. 6 schematically shows lights 52a, 52b, 52c, 52d which arerespectively incident to a substrate 51 having light transmittance andlight diffusibility. The light diffusibility of the substrate 51 appearsbecause of the diffusion of light inside the substrate 51. In FIG. 6,the light diffusibility is illustrated as sharp change of directions ofthe lights inside the substrate 51. Such diffusing phenomenon is causedby discontinuity of refractive index at interfaces between fineparticles.

When the lights are changed in directions, a part of the lights, such asa light 53a is emitted outside from the surface of the substrate 51.This is phenomenally similar to the surface reflection. Other lightssuch as the lights 54b, 54c and 54d are emitted from the back surface ofthe substrate 51, and they are transmitted lights.

Although FIG. 6 schematically shows a light by a single line, it isnoted that for example, the entire incident light 52d does notnecessarily form the optical path denoted by the line shown in FIG. 6 tobe emitted but a part of the light 52d is emitted, because thereactually occurs diffusion of light inside the substrate 51 with acertain probability. However, the following typical expression issufficient for explaining the light, and the probability problem is notreferred to in this explanation.

FIG. 7 shows light absorption bodies 62 formed at a part of the surface(incident side) of the substrate 51 in addition to the structure of FIG.6.

In FIG. 7, supposing that the lights 52a, 52b, 52c and 52d shown in FIG.6 respectively form the optical paths inside the substrate 51 like thecase of FIG. 6, the lights 52a, 52b and 52d which travel along thesurface of the substrate 51 are respectively absorbed by the lightabsorption bodies 62 as evident from FIG. 7 in the midway of therespective optical paths, then they are finally changed to heat.

That is, in the structure of FIG. 7, the lights are not emitted from thesubstrate 51 like the lights 54b, 54c and 54d as shown in FIG. 6.However, the light incident to the substrate 51 as the light 52c doesnot meet the light absorption bodies 62 in the course of traveling sothat it is emitted from the back surface of the substrate 51 as thelight 54c like the case of FIG. 6.

FIG. 8 shows light reflection bodies 73 each made of a metallic materialand replaced with the light absorption bodies 62 of FIG. 7.

Supposing the lights 52a, 52b, 52c and 52d shown in FIG. 6 respectivelyform the optical paths inside the substrate 51 like the case of FIG. 6,lights incident from the inside of the substrate 51 to the lightreflection bodies 73 are reflected substantially 100% and are returnedto the inside of the substrate 51. Accordingly, the lights which areincident as the lights 52a, 52b, 52c and 52d are respectively emittedfrom the back surface of the substrate 51 as the lights 54a, 54b, 54cand 54d.

As for the light 54a, although it is emitted from the back surface ofthe substrate 51, there is good possibility that it is emitted from thefront surface of the substrate 51 depending on the course of diffusioninside the substrate 51.

Let us consider as follows by applying the above explanation of theprinciple to the solar battery powered watch of the second embodiment ofthis invention.

The dial 4 shown in FIG. 5 corresponds to the substrate 51 shown inFIGS. 6 through 8. When the dial patterns 10 are directly formed on thesurface of the dial 4 (without interposing the light reflection layers11), the dial patterns 10 correspond to the light absorption bodies 62of FIG. 7, from which it is evident that light absorption phenomenon asexplained in FIG. 7 will occur.

Meanwhile, in the second embodiment in which the dial patterns 10 areformed on the surface of the dial 4 by way of the light reflectionlayers 11 (see FIG. 5), the light reflection layers 11 correspond to thelight reflection bodies 73 of FIG. 8 from which it is understood thatthe light reflection phenomenon as explained in FIG. 8 will occur.

As is evident from the above explanations, in the structure includingthe dial patterns 10 which are formed on the dial 4 having lighttransmittance and light diffusibility without interposing the lightreflection layers 11, a part of the incident lights is absorbed by thedial patterns 10 and it is attenuated.

On the other hand, according to the second embodiment having the lightreflection layers 11, most of lights which are incident to the dial 4can transmit to the back surface of the substrate 51 without beingattenuated. That is, it is possible to eliminate loss of light caused byabsorption of light at the interface between the dial 4 and the dialpatterns 10, and also it is possible to reduce the amount of lightirradiating the solar battery 3 to a minimum.

Particularly, a part of the lights, which is incident to the dial 4 atthe peripheries of the dial patterns 10 and is diffused horizontally, iseasily absorbed by the dial patterns 10, so that the amount of lightreaching the solar battery is further attenuated by the amountcorresponding to several times as large as that of an area ratio(normally about 5%) of the dial patterns 10 relative to the dial 4,thereby exerting an non-negligible influence upon the solar batterypowered watch provided with the solar battery 3. The light reflectionlayers 11 provided in the second embodiment performs such function andeffect that they suppress the attenuation of the amount of transmittedlight, and increase the amount of light irradiating the solar battery 3.

FIG. 9 is a view of a solar battery powered watch according to anothermodification of the second embodiment.

That is, a transparent substrate 81 is provided in addition to theconstituent of FIG. 8, and the light reflection body 73 is formed on thefront surface of the transparent substrate 81. An incident light 52e,shown as an example, travels directly inside the transparent substrate81, and is diffused inside the substrate 51, then it is returned to thetransparent substrate 81, then it travels directly inside thetransparent substrate 81, and then it is reflected on the lightreflection body 73. Thereafter, the incident light 52e travels directlyinside the transparent substrate 81, and is diffused inside thesubstrate 51, and finally it is emitted from the back surface of thesubstrate 51 as the emitted light 54e.

Incidentally, since only the substrate 51 has light diffusibility, thetransparent substrate 81 plays a role to permit the light to directlytravel therein.

When the structure shown in FIG. 9 is applied to the dial 4, atransparent substrate having direct light traveling property islaminated to the surface of the substrate 51 made of ceramic, and thedial patterns 10 are formed on the surface of the transparent substrateby way of the light reflection layers 11. Even in such a structure, itis possible to prevent light from being absorbed by the dial patterns sothat the light can sufficiently irradiate the solar battery 3. Further,such a change of structure has an effect that a free designing of thedial for the solar battery powered watch can be enhanced.

Next, a method of forming the light reflection layers 11 and the dialpatterns 10 on the dial 4 will be described in detail.

After the dial 4 was fabricated by the method of fabricating the dial,which was explained in the first embodiment, the light reflection layers11 are formed on the surface of the dial 4.

That is, the light reflection layers 11 are formed on the dial patterns10 using ink composed of powdered gold which is dispersed in and mixedwith varnish by a tampon printing method. Thereafter, the lightreflection layers 11 are temporally dried at the temperature of about100° C., further it is sintered by a heat of about 750° C. so that onlygold is sintered to form the light reflection layers 11.

Finally the tampon printing is applied to the surface of the lightreflection layers 11 using UV hardening type ink of black pigment, andit is temporally dried at the temperature of about 80° C., then it isirradiated with UV rays to completely solidify the light reflectionlayers 11.

The dial 4 which was fabricated with the above steps is incorporatedinto the case 1 shown in FIG. 1. As a result, inoperative condition suchas stop of the watch which will be caused by the shortage of generatedelectric power of the solar battery 3 does not occur, and the watchremains operative normally. Furthermore, the dial was natural white incolor.

The area ratio of the dial patterns 10 relative to the dial 4 is 4.3%,and the light transmittance of the dial 4 is 51% before the lightreflection layers 11 and the dial patterns 10 are formed, and it is 49%after the light reflection layers 11 and the dial patterns 10 wereformed.

As for the dial as a comparative example, which was fabricated byomitting the printing step using ink composed of powdered gold which isdispersed in and mixed with varnish among the aforementioned steps, thelight transmittance is 51% before the dial patterns are formed and it is42% after the dial patterns were formed.

Although in the second embodiment set forth above, the light reflectionlayers 11 are interposed between the dial 4 and the dial patterns 10,the back surfaces of the dial patterns (surfaces contacting the dial 4)become the light reflection faces if the dial patterns 10 per se areformed of the light reflective material. Even such light reflectionfaces can reflect the scattered light inside the dial 4 to the solarbattery 3, so that they can achieve the same effect as the lightreflection layers 11.

(Third Embodiment)

A solar battery powered watch according to a third embodiment of thisinvention will be now described.

The feature of the third embodiment resides in fixing means of the dial4 (covering member) in the case 1 and positioning means relative to themovement 2 in the solar battery powered watch shown in FIG. 1. The otherentire structure and the method of fabricating the solar battery, andthe method of fabricating the dial are the same as those of the firstembodiment (see FIG. 1), and hence the detailed explanations thereof areomitted while numerals in figures are denoted in common with those ofthe first embodiment.

FIG. 10 is a cross sectional view of the solar battery powered watchaccording to the third embodiment, and FIG. 11 is a plan view of a dial(covering member) and a positioning frame which are respectivelyconstituents of the solar battery powered watch.

As shown in FIG. 11, recessed parts 12 and 13 each having a circularshape or a rectangular shape are provided on the dial 4 at positionsclose to the dial patterns 10 which indicate twelve o'clock and sixo'clock, Meanwhile, projecting parts 14 and 15 which are engaged in therecessed parts 12 and 13 are formed in the positioning frame 8.

The positioning frame 8 is made of a resin material or a metallicmaterial, and it is arranged on the upper surface of the solar battery 3at the outer periphery of the dial 4. The positioning holes 8a and 8bare respectively bored in the positioning frame 8 while the positioningpins 2a and 2b are respectively provided on the front face of themovement 2 at the outer periphery thereof. The positioning pins 2a and2b penetrate the solar battery 3 and protrude to the surface of thesolar battery 3. The positioning frame 8 can be positioned relative tothe movement 2.

If the dial 4 is arranged in a state where the projecting parts 14 and15 are engaged in the recessed parts 12 and 13, the dial 4 can bepositioned relative to the movement 2 by way of the positioning frame 8.

Meanwhile. the surfaces of the dial 4 and the positioning frame 8 areflush with each other, and the surface of the positioning frame 8 whichcontacts the case 1 is flush with the case 1 awhile the dial 4 and thepositioning frame 8 are aligned with each other in height.

The movement 2, the solar battery 3 and the outer periphery of thepositioning frame 8 are respectively held by a frame body 16 and theyare accommodated in the case 1 while keeping this holding state. Whenthe frame body 16 is pressed against the face side opening 1a of thecase 1 by the case back 6, the positioning frame 8 and the dial 4contact a peripheral sidewall 17 of the face side opening 1a of the case1.

If the state where the dial 4 and the positioning frame 8 contact theperipheral sidewall 17 of the case 1 is maintained, there is nolikelihood of breakage of the dial 4 and the positioning frame 8 causedby striking against the peripheral sidewall 17 even if they receive alarge impact loading, thereby enhancing the impact tolerance.

As compared with the case where the projecting parts 4a and 4b shown inFIG. 2 are formed on the dial 4 made of a fragile material such asceramic and they are engaged in the recessed parts 8c and 8d of thepositioning frame 8, the recessed parts 12 and 13 are provided on thedial 4 so that the stress concentration occurs in the projecting parts4a and 4b, thereby preventing the dial 4 from being cracked and broken,and further enhancing the impact tolerance.

FIG. 12 is a cross sectional view of a modification of the thirdembodiment.

In this embodiment, only the dial 4 contacts the peripheral sidewall 17of the face side opening 1a of the case 1, and a gap is defined betweenthe positioning frame 8 and the peripheral sidewall 17. That is, theheight of the positioning frame 8 is set to be lower than that of thedial 4.

When the positioning frame 8 is made of a metallic material which isless fragile the same impact tolerance can be obtained in the same wayas the third embodiment.

FIG. 13 is a cross sectional view of another modification of the thirdembodiment.

In this modification, an elastic member 18 is provided between the dial4, the positioning frame 8 and the solar battery 3. The elastic member18 is made of rubber or synthetic resin respectively having elasticity,and it has a thickness ranging from 50 to 100 μm. Since the elasticmember 18 is interposed as set forth above, it is possible to prevent amechanical breakage caused by the striking of the dial 4 and thepositioning frame 8 against the light receiving surface 3a of the solarbattery 3 and possible to enhance the impact tolerance of the dial 4owing to an impact or shock absorbing effect by the elastic member 18.

The elastic member 18 may be provided between the dial 4, thepositioning frame 8 and the solar battery 3 in the structure of themodification in FIG. 12.

As a result of impact tests for the solar battery powered watch havingthe structures shown in FIGS. 10, 11 and 12 which test corresponds to afree drop of watch from the height of 1 m, the dial 4 is not at allbroken.

In the positioning structure of the dial 4 shown in FIG. 11, therecessed parts 12 and 13, and the projecting parts 14 and 15 may beprovided appropriately at three points or more on the dial 4.

(Fourth Embodiment)

A solar battery powered watch according to a fourth embodiment of thisinvention will be now described with reference to FIGS. 14 and 15. FIG.14 is a cross sectional view of the solar battery powered watch of thefourth embodiment, and FIG. 15 is a plan view of a covering member whichis one of the constituents of the solar battery powered watch and isused as a dial.

In FIGS. 14 and 15, constituents which are the same as or correspond tothose in FIGS. 1 and 2 are denoted by the same numerals, and theexplanations thereof are omitted.

The glass 5 is attached to the face side opening 1a of the case 1 by wayof a first packing 20 made of a resin material, thereby forming anairtight structure to prevent the entry of dust, moisture and the liketo the solar battery powered watch.

The ornamental frame 21 is fixed to the inner side of the case 1 alongthe periphery of the face side opening 1a of the case 1. The ornamentalframe 21 covers the periphery (rough surface) of the face side opening1a of the case 1 which is a forged product, and it has beenconventionally employed for enhancing the ornamental value of the watch.The ornamental frame 21 is generally made of a material which isdifferent from that of the case 1, and it has a mirror-finished surfaceformed by grinding the surface thereof by a diamond tool.

Further, a groove is defined in the case 1 at the surface to which thecase back 6 is attached, and a second packing 22 made of a rubbermaterial is provided in the groove. The case back 6 is mounted to thecase 1 by way of the second packing 22, thereby forming an airtightstructure to prevent the entry of dust, moisture and the like to thesolar battery powered watch.

The movement 2, the dial 4 and the solar battery 3 are accommodated inthe case 1 in the state where they are held by a casing frame 23 at theouter peripheries thereof. The casing frame 23 is made of a resinmaterial. A stage part 23a having the same dimensions as the thicknessof dial 4 is formed on the stage part 23a at the front end thereof,wherein the dial 4 which is engaged in the positioning frame 8 (see FIG.15) is accommodated in the stage part 23a to be dropped therein.Accordingly, the front end of the casing frame 23 is flush with thesurface of the dial 4.

An accommodation part 23b of the solar battery 3 is defined in thecasing frame 23 under the stage part 23a for accommodating the dial 4therein. The solar battery 3 is arranged in the accommodation part 23b.

The lower end surface 21a of the ornamental frame 21 protrudes under(the back side of) the peripheral sidewall 17 of the face side opening1a of the case 1 shown in FIG. 14. Accordingly, the casing frame 23 forholding the dial 4, the solar battery 3 and the movement 2 is pressed bythe case back 6 from the back side, the inner face of the periphery ofthe dial 4 is brought into contact with the ornamental frame 21.

At this time, if the lower end surface 21a of the ornamental frame 21 ispositioned under (the back side of) a curved part 25 which is formed bya forging process on the base of the peripheral sidewall 17, the casingframe 23 is not liable to interfere with the curved part 25. When thedial 4 contacts the ornamental frame 21, a gap 24 is defined between theback of the peripheral sidewall 17 of the case 1 and the dial 4. Sincethe curved part with a thickness of about 0.2 mm is formed with cornersin a general forging process, if the gap 24 having a length of about 0.2mm is defined between the back of the peripheral sidewall 17 of the case1 and the dial 4, it is possible to prevent the interference between thecurved part 25 and the casing frame 23.

Since the projecting parts 4a and 4b formed at the periphery of the dial4 (see FIG. 15) are disposed in the gap 24, even if impact loading isapplied from the outside, the projecting parts 4a and 4b do not strikeagainst the case 1. Accordingly, there is no likelihood of occurrence ofstress concentration in the projecting parts 4a and 4b, therebypreventing the dial 4 from being cracked and broken, and furtherenhancing the impact tolerance.

The inventors of this application fabricated 10 solar battery poweredwatches each having the structure shown in FIG. 14, and these solarbattery powered watches are subject to a hammer impact testcorresponding to a free drop from the height of 1 m. As a result of thetest, no dial 4 was broken.

FIG. 16 is a view for explaining a modification of the fourthembodiment.

The solar battery powered watch shown in FIG. 16 has an intermediatemember 26 made of a resin material between the movement 2 and the caseback 6. The intermediate member 26 may be fixed to the case back 6. Itis preferable that the inner diameter of the intermediate member 26 issubstantially the same as that of the ornamental frame 21 and theintermediate member 26 is opposite to the ornamental frame. With such anarrangement, a repulsive force which is generated between the ornamentalframe 21 and the intermediate member 26 does not act on the constituentssuch as the movement 2, the solar battery 3 and the dial 4 as a shearingforce.

Meanwhile, when the case back 6 is attached to the case 1, it isstructured not to define a gap between the intermediate member 26 andthe movement 2. In order to structure it as such, the thickness of theintermediate member 26 may be greater than the length of the gap betweenthe movement 2 and the case back 6 by the length ranging from about 0.5mm to 0.1 mm.

When the case back 6 is attached to the case 1, the dial 4 is broughtinto contact with and fixed to the ornamental frame 21 owing to thepressing force from the intermediate member 26. With the provision ofthe intermediate member 26, when solar battery powered watch receivesthe impact loading, the intermediate member 26 operates to suppress thedeformation of the dial 4 to surely prevent the breakage of the dial 4.

FIG. 17 is a view for explaining another modification of the fourthembodiment.

The solar battery powered watch shown in FIG. 17 has an elastic member27 such as rubber which is interposed between the casing frame 23 andthe case back 6. The elastic member 27 may be fixed to the lower endsurface of the casing flame 23. When the case back 6 is mounted to thecase 1, the case back 6 is structured to press the elastic member 27,and the dial 4 is brought into contact with the ornamental frame 21without generating a gap there between by the pressing force from thecase back 6.

The operation of the elastic member 27 will be now described. That is,if the solar battery powered watch has not the elastic member 27, whenit receives impact loading from the outside repetitively, the case back6 made of the metallic material transmits the impact loading to thecasing frame 23 repetitively. The casing frame 23 is made of a resinmaterial as set forth above. Accordingly, the casing frame 23 isdeformed when it receives the impact loading repetitively, so that a gapis defined between the casing frame 23 and the case back 6.

As a result, a gap is also defined between the surface of the dial 4 andthe case 1 and between the case 1 and the ornamental frame 21. When thesolar battery powered watch receives impact loading, the dial 4 strikesstrong against the ornamental frame 21 so that the dial 4 is broken.

The elastic member 27 is provided as an impact absorbing member betweenthe casing frame 23 and the case back 6 in order to prevent thedeformation of the casing frame 23 caused by repetitive impact loading.When the elastic member 27 is provided, the deformation of the casingframe 23 owing to the impact loading is prevented, thereby preventingthe breakage of the dial 4.

At though not shown in FIG. 17, the intermediate member 26 shown in FIG.16 may be also provided between the case back 6 and the movement 2.

FIG. 18 is a view for explaining still another modification of thefourth embodiment.

The feature of the solar battery powered watch in FIG. 18 resides in apositioning fixed means for positioning and fixing the dial 4 relativeto the movement 2. That is, in this modification, the projecting parts4a and 4b are not formed on the dial 4 shown in FIG. 15, but a pluralityof (e.g., two) through holes are bored in the dial 4 at a regioncontacting the ornamental frame 21 and end portions of fixed pins 28 areengaged in the through holes. The dial 4 is positioned relative to themovement 2 using the fixed pins 28.

Through holes through which the fixed pins 28 penetrate are bored in thesolar battery 3, and positioning holes (fixing means) in which the fixedpins 28 are engaged are bored in the movement 2. The fixed pins 28 areengaged in the positioning holes of the movement 2 by way of the throughholes of the solar battery 3, so that the dial 4 are positioned relativeto and fixed to the movement 2, and the solar battery 3 is alsopositioned relative to the movement 2.

Although not shown in FIG. 18, the intermediate member 26 shown in FIG.16 may be provided between the movement 2 and the case back 6. Further,the elastic member 27 shown in FIG. 17 may be provided between the caseback 6 and the casing frame 23. Still further, the intermediate member26 and the elastic member 27 are respectively provided.

Although the size of the dial 4 is substantially the same as that of themovement 2 in FIG. 18, these sizes are not necessarily the same. Thatis, the stage part 23a is formed on the casing frame 23 and the dial 4is accommodated and disposed in the stage part 23a shown in FIG. 14.

Although the size of the dial 4 is substantially the same as that of thesolar battery 3 in FIG. 18, the solar battery 3 may be made smaller thanthe dial 4 and it may be accommodated and disposed in the accommodationpart 23b (see FIG. 14) of the casing frame 23. In this case, it ispreferable that the dimensions of the solar battery 3 are substantiallythe same as or slightly greater than outer dimensions of the ornamentalframe 21.

That is, when the solar battery powered watch receives the impactloading from the outside, the impact loading is transmitted to the dial4 by way or the movement 2. At this time, when the dimensions of thesolar battery 3 are smaller than the outer dimensions of the ornamentalframe 21, a shearing force is applied to the dial 4 so that the dial 4is liable to be broken. Accordingly, if the dimensions of the solarbattery 3 are made larger than the outer dimensions of the ornamentalframe 21, such a shearing force does not apply to the dial 4, therebypreventing the breakage of the dial 4.

As the fixed means for fixing the dial 4 and the solar battery 3relative to the movement 2, it is possible to employ means other thanthe fixed pans 28 for adhering respective constituents, for example, anadhesive. In case that the solar battery 3 and the dial 4 are adhered toeach other, it is possible to suppress the lowering of generatedelectric power of the solar battery 3 if only the periphery of the solarbattery 3 is adhered by the adhesive.

In the aforementioned embodiments, the case 1 and the ornamental frame21 are respectively formed of different members but they may as well beintegrally formed.

CAPABILITY OF EXPLOITATION IN INDUSTRY

This invention can be utilized for various watches incorporating a solarbattery therein as a power supply, thereby enhancing an ornamental valuethereof and also enhancing light transmittance relative to the solarbattery,

What is claimed is:
 1. A solar battery powered watch comprising a casehaving an opening on a front side thereof, and a glass covering theopening, a movement having a hand-driving mechanism and housed in thecase, a solar battery having a light receiving surface disposed oppositeto the glass and installed on a front side of the movement inside thecase, and a covering member for covering the light receiving surface ofthe solar battery,characterized in that the covering member is formed bymolding ceramic containing alumina as a main constitute wherein anaverage diameter of the ceramic grains ranges from 5 μm to 40 μm, andthe covering member is molded to a thickness ranging from 0.2 mm to 0.5mm.
 2. A solar battery powered watch comprising a case having an openingon a front side thereof, and a glass covering the opening, a movementhaving a hand-driving mechanism housed in the case, a solar batteryhaving a light receiving surface disposed opposite to the glass andinstalled on a front side of the movement inside the case, and acovering member formed by molding ceramic for covering the lightreceiving surface of the solar battery;characterized in that optionaldial patterns are formed on a surface of the covering member, and lightreflection layers or light reflection faces are interposed between thesurface of the covering member and the dial patterns.
 3. A solar batterypowered watch, comprising a case having an opening on a front sidethereof, and a glass covering the opening, a movement having ahand-driving mechanism housed in the case, a solar battery having alight receiving surface disposed opposite to the glass and installed ona front side of the movement inside the case, and a covering memberformed by molding ceramic for covering the light receiving surface ofthe solar battery;characterized in that a transparent substrate islaminated to the surface of the covering member, and optional dialpatterns are formed on the surface of the transparent substrate, lightreflection layers or light reflection faces being interposed between thesurface of the transparent substrate and the dial patterns.
 4. The solarbattery powered watch according to claim 1, characterized in that anouter rim of the covering member is kept in contact with a peripheralsidewall of the opening of the case.
 5. The solar battery powered watchaccording to claim 4, characterized in that:a positioning frame disposedaround the periphery of the covering member has projecting parts orrecessed parts while the covering member has recessed parts orprojecting parts for engagement with the projecting parts or therecessed parts of the positioning frame; and the watch furthercomprising a means for positioning the positioning frame relative to themovement.
 6. The solar battery powered watch according to claim 1,characterized in that:an ornamental frame is fixedly mounted inside theperiphery of the opening of the case and inside of the periphery of thecovering member is supported by the ornamental frame.
 7. The solarbattery powered watch according to claim 6, characterized in that:apositioning frame is disposed around an outer periphery of the coveringmember, recessed parts are formed in the positioning frame, andprojecting parts are formed in a periphery of the covering member forengagement with the recessed parts of the positioning frame; and a gapis defined between the periphery of the covering member and the case,and the projecting parts formed on the periphery of the covering memberis disposed in the gap.
 8. The solar battery powered watch according toclaim 6, characterized in further comprising:a backside opening formedon a back side of the case, a casing frame for securely holding thecovering member, the solar battery, and the movement inside the case,and an intermediate member composed of a resin material, disposedopposite to the ornamental frame, and interposed between the case backcover and the movement without defining a gap therebetween.
 9. The solarbattery powered watch according to claim 6, characterized in that;thecase has a back side opening on a back side thereof; and a casing framefor securely holding the covering member, the solar battery, and themovement inside the case, and a case back cover for covering the backside opening, the case further comprising an elastic member interposedbetween the case back cover and the casing frames.
 10. The solar batterypowered watch according to claim 6, characterized in that:through holesare defined in the covering member at a region contacting the ornamentalframe, and end portions of fixed pins are engaged in the through holes,and the fixed pins protrude from the underside of the covering member,and through-holes are bored in the solar battery for insertion of thefixed pins, and further a means for securely holding the fixed pins isprovided on the movement.